1. Field of the Invention
The present invention relates to riding mowers for use on golf courses and other large grounds, and, more particularly, relates to riding mowers having a mechanism for leveling the cutting heads as they engage the ground.
2. Discussion
The assignee of the present invention manufacturers and sells riding mowers for turf maintenance. More particularly, the assignee sells both electrically and hydraulically operated mowers for turf maintenance. An example of the all-electric riding greens mower is described in detail in the commonly-assigned patents U.S. Pat. No. 5,406,778, issued Apr. 18, 1995; U.S. Pat. No. 5,540,037, issued Jul. 30, 1996; and U.S. Pat. No. 5,553,445, issued Sep. 10, 1996, the disclosures of which are hereby incorporated by reference.
On almost all golf courses, both greens and fairways must be cut to a height which is typically much lower than the average cut height of the lawn which may be found in a typical garden. Most fairways are cut to a height of 0.50 inches, and most greens are cut to a shorter height of approximately 0.18 inches. In order to achieve such low cut heights, greens superintendents typically employ reel mowers as are commonly known in the art. Fairways are normally cut using a gang mower having at least three or more reel type cutting heads trailed behind a tractor or integrated into a riding mower. Previously, most greens were cut using specialized, walking greens mowers operated by a user walking behind the mower. In order to cut costs and to reduce daily maintenance periods in order to maximize golf course usage, more and more golf courses are employing riding greens mowers so that one maintenance person can cut more greens in less time. Such riding greens mowers may either be electric, as described in the above-referenced patents, hydraulic, or a combination of electric and hydraulic.
Whether operating a walking or riding greens mower, the greens superintendent typically guides the mowers to traverse the green in adjacent rows and makes a finish cut around the edge of the golf green. When operating a riding greens mower, as the mower approaches the edge of the green, the operator raises the cutting heads so that the mowing heads do not cut into the fringe of the green. The operator then turns the mower to begin cutting the next, adjacent row. When the mower is in position to begin cutting the adjacent row, the operator lowers the cutting heads onto the green and traverses the green.
Most reel-type cutting heads pivot about a horizontal axis so that they can follow the contour of the green. Although this pivoting motion is desirable while the mower engages the ground, this motion may be undesirable while the cutting head is being lowered to actually engage the ground. Preferably, the mower is completely level just as it contacts the ground. When the mower is not level, the side of the mower striking the ground first bounces upward from the green causing the opposite side to lower to the green. This opposite also bounces upward causing the first side to rebound before the mower settles onto the green. This bounce and rebound effect sometimes results in the reels of the cutting head undesirably scalping the green as it engages the ground.
This phenomena is further exacerbated by the present typical design of both electric and hydraulic riding greens mowers. In most riding greens mower, the cutting heads, whether left front, right front, or center cutting heads, are substantially identical. The cutting heads attach to the reel mower via a pull frame, and a motor, whether electric or hydraulic, mounts to one side of the cutting head for driving the reel. This arrangement typically requires an initial, static balancing in order to counter-balance the weight of the hydraulic or electric motor. Further, the motors often have either electric or hydraulic control lines which exert dynamic forces which may change during the raising and lowering of the cutting head.
When the cutting heads are raised and lowered, the forces exerted by the electric or hydraulic lines attached to the motor may vary the balance of the cutting head dynamically, causing the cutting head to rock or sway about a horizontal pivot point. These forces cannot be counter-balanced by merely using weights at an opposite of the mower. This minor change in dynamic balance may result in the above-described scalping phenomenon. Further, with respect to a triplex mower, the left front and right front cutting heads often have different balance characteristics because of various routings of hydraulic or electrical control lines and because of different characteristics exhibited by the left and right front cutting heads when raised. This problem may be further exacerbated when raising or lowering the mower heads while completing a left hand or right hand turn, depending upon the design of the particular mower and inertial forces introduced during the turning operation. The cumulative effect of these dynamic imbalances is a sway of the mower head about a horizontal axis during the lowering operation. This sway may result in the above-described scalping effect.
Therefore, it is an object of the present invention to provide a leveling mechanism which maintains the cutting head substantially level when the cutting head is off the ground.
It is a further object of the present invention to provide a leveling mechanism which maintains the cutting head substantially level as the cutting head engages the ground and as the cutting head disengages the ground.
It is yet a further object of the present invention to provide a linkage for maintaining the cutting head substantially level as the cutting head is lowered to engage the ground.
It is yet a further object of the present invention to provide a parallel linkage for maintaining the cutting head substantially level as the cutting head engages the ground.